Uccaiḥśravā (Ucchaihsrava) is the greatest among horses. As Airāvata (Airavata) is the greatest among elephants, so is Uccaiḥśravā. The term ‘śravas’ (sravas) means the hearing organ. So, Uccaiḥśravā can mean ‘one who has long ears’. The ears of this horse were well-shaped. Another meaning Uccaiḥśravā can be ‘one whose high fame is heard from a distance. Since this horse is the greatest of all horses, and highly famous, it is called Uccaiḥśravā.
There are several legends regarding the emergence of Uccaiḥśravā. In the legend of Amṛtamanthana as described in Rāmāyaṇa (Ramayana), Mahābhārata (Mahabharata) and other Purāṇa(s) (Purana; Mythological Scrptures), it is said that during Samudramanthana (churning of the sea) Uccaiḥśravā emerged from the bottom of the sea.
However, Vāyupurāṇa(Vayupurana) and Brahmāṇḍapurāṇa (Brahmandapurana) mention that Gāndharvī (Gandharvi), daughter of Surabhi, was the mother of all horses. Uccaiḥśravā and other distinguished horse were born of the womb of Surabhi.

In the Mahākāvya (Mahakavya; epic)and Purāṇa(s), Uccaiḥśravā , after emerging from the sea, resides with the gods in svarga (heaven). He is known as an inhabitant of the heavenly abode, and most people know him as the horse of Indra, king of gods. But in Mahākāvya and Purāṇa(s), Indra is found to ride on Airāvata several times, but there is no mention that he is riding on Uccaiḥśravā. The use and preservation of horses was a major contribution of the Aryan civilisation. Perhaps because of this reason,the name of Indra, the ancient god of the Aryan civilisation, comes in association with Uccaiḥśravā. However, in one śloka of Rāmāyaṇa, Uccaiḥśravā is mentioned as one of the horses of the chariot of the Sun-god.

In Mahābhārata, in the legend of Kadrū (Kadru) and Vinatā (Vinata), the role of Uccaiḥśravā is very important, though in an indirect way. Kadrū and Vinatā, daughters of Dakṣa prajāpati, were the two wives of Kaśyapa (Kasyapa). There was little friendship between them, rather they sought to humiliate each other at the slightest pretext. One day Kadrū asked Vinatā, ‘Can you tell me, what is the colour of Uccaiḥśravā?’ Vinatā anwered casually, ‘It’s pure white’. Then she added, ‘If you think otherwise, tell me so. Let’s have a bet. The one whose answer will be wrong, will serve as the maid of the winner’. Kadrū had an evil plan. She said, ‘Le it be so. But I think, the whole body of Ucchaiḥśravā is white, but his tail is black’. It was decided that the next morning, they would be going to see Uccaiḥśravā. Kadrū then asked her serpent-sons, “Cover the tail of Uccaiḥśravā in such a way that it looks black”. Most of her sons obeyed the mother. But some of them did not agree to do this unfair act. Kadrū cursed them that they would be burned to death in the Sarpayajña (Sarpayajna) of Janamejaya.

But the obedient sons of Kadrū followed her instruction so well, that the nest morning, when Kadrū and Vinatā went to see Uccaiḥśravā, they found its tail black. After this, Kadrū served as the maid of Vinatā for 500 years.